A light valve projector projects a bright light source through an electro-optical system that receives electronic image information and produces a projected optical image. Light-valve projectors are rapidly converting to matrix driven arrays; examples being active-matrix LCD projectors such as the projector disclosed in U.S. Pat. No. 5,231,432 and the DMD projector of Texas Instruments Company which uses technology originating from the type of solid state light modulator disclosed in U.S. Pat. 3,882,271. Projectors of this type employ a diffraction grating, and a substantial fraction of the light is diffracted by the electrode pattern itself. Typically 30% of the incident light is diffracted by the electrode pattern. This not only reduces the optical efficiency, it also reduces the maximum contrast ratio that can be obtained. The conventional solution is to use a small aperture projection lens in order to get better contrast. This severely limits the light output for a given panel size. On all but highly coherent laser sources the light output is limited by the intrinsic brightness of the light source, the panel clear aperture area, and the projection lens aperture.
It is among the objects of the present invention to provide a solution to the indicated limitations of the prior art, and to generally improve operation of light valve projectors that employ a diffraction grating.